Fleet-carrier development without treaty conversions

What would the first purpose-built fleet carriers have looked like if treaty conversions had not occurred?

Evidence is limited, but cruiser-sized experimental carriers likely would have preceded later Soryu- or Hiryu-like fleet carriers, whose arrival might be delayed by capital-ship construction.

Firm plans are scarce because carrier design was still experimental, leaving Hosho as the main Japanese starting point in this counterfactual. Major shipyards would also have been occupied by the planned sixteen-ship capital program, limiting space and resources for large purpose-built carriers. Cruiser-sized carriers offer a plausible intermediate step from which designers could gain operating experience. Japanese ships resembling Soryu and Hiryu might still emerge as the first mature fleet carriers, but their timing would depend on the lessons from those smaller vessels and the burden of competing construction.